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denoland-deno/ext/napi/value.rs
snek 3765e6b3a6
fix: clean up some node-api details (#24178)
- fix a few napi_* types
- clean up env hooks
- implement blocking queue in tsfn
- reduce transmutes
- use new `DataView::new` api from rusty_v8
2024-06-11 17:40:44 -07:00

69 lines
1.8 KiB
Rust

// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
use deno_core::v8;
use std::mem::transmute;
use std::ops::Deref;
use std::os::raw::c_void;
use std::ptr::NonNull;
/// An FFI-opaque, nullable wrapper around v8::Local<v8::Value>.
/// rusty_v8 Local handle cannot be empty but napi_value can be.
#[repr(transparent)]
#[derive(Clone, Copy, Debug)]
pub struct NapiValue<'s>(
Option<NonNull<v8::Value>>,
std::marker::PhantomData<&'s ()>,
);
pub type napi_value<'s> = NapiValue<'s>;
impl<'s> Deref for napi_value<'s> {
type Target = Option<v8::Local<'s, v8::Value>>;
fn deref(&self) -> &Self::Target {
// SAFETY: It is safe to transmute `Option<NonNull<T>>` to `Option<*const T>`.
// v8::Local guarantees that *const T is not null but napi_value *can* be null.
unsafe { transmute::<&Self, &Self::Target>(self) }
}
}
impl<'s, T> From<v8::Local<'s, T>> for napi_value<'s>
where
v8::Local<'s, T>: Into<v8::Local<'s, v8::Value>>,
{
fn from(v: v8::Local<'s, T>) -> Self {
Self(Some(NonNull::from(&*v.into())), std::marker::PhantomData)
}
}
impl<'s, T> From<Option<v8::Local<'s, T>>> for napi_value<'s>
where
v8::Local<'s, T>: Into<v8::Local<'s, v8::Value>>,
{
fn from(v: Option<v8::Local<'s, T>>) -> Self {
if let Some(v) = v {
NapiValue::from(v)
} else {
Self(None, std::marker::PhantomData)
}
}
}
const _: () = {
assert!(
std::mem::size_of::<napi_value>() == std::mem::size_of::<*mut c_void>()
);
// Assert "nullable pointer optimization" on napi_value
unsafe {
type Src<'a> = napi_value<'a>;
type Dst = usize;
assert!(std::mem::size_of::<Src>() == std::mem::size_of::<Dst>());
union Transmute<'a> {
src: Src<'a>,
dst: Dst,
}
Transmute {
src: NapiValue(None, std::marker::PhantomData),
}
.dst
};
};